Whoever is elected president on Nov. 4 is expected to name at least one new justice to the US Supreme Court, and perhaps as many as three.

With the nine-member court closely divided on hot-button issues like abortion, affirmative action, and the death penalty, a change in personnel could set the stage for big changes in the law. Despite such high stakes, the future of the court has yet to emerge as a central election issue.

The justices most likely to retire during the next four years, legal analysts say, are all members of the court’s liberal wing: John Paul Stevens, Ruth Bader Ginsburg, and David Souter. That means should John McCain replace a sitting liberal justice with a conservative justice, the balance of power on the court could shift decisively to the right on key issues. On the other hand, should Barack Obama replace a sitting liberal justice with a liberal nominee, the balance of power on the court would likely remain largely unchanged.

But Senator Obama’s first appointment need not be a mere place holder, some analysts say. He could use the nomination to appoint a relatively young, progressive justice capable of going head-to-head with conservative Chief Justice John Roberts for the next 20 to 30 years.

“The long-term trajectory of the court is in play,” says Richard Garnett, a constitutional law professor at Notre Dame. “[Obama] is going to want to appoint the next [William] Brennan or a left-leaning version of John Roberts.”

On the other side, any nomination by Senator McCain would have to survive not only a Democratic Senate hostile to a strong conservative but also an aggressive Republican base that chewed up President Bush’s Harriet Miers nomination because she wasn’t considered a heavyweight conservative.

The lack of significant campaign discussion over the Supreme Court has been noticeable. Questions about the court seemed an afterthought in last week’s debate. But in his recent endorsement of Obama, former Secretary of State Colin Powell, a Republican, included the future of the court as a reason he was supporting the Democratic nominee.

“I would have difficulty with two more conservative appointments to the Supreme Court, but that’s what we’d be looking at in a McCain administration,” Mr. Powell said on NBC’s “Meet the Press.”

The retired general is a supporter of affirmative action and has praised its effectiveness in the military. The conservative wing of the court has narrowed the use of affirmative action in recent years.

McCain and Obama have staked out sharply different positions on the kinds of judges and justices they would appoint.Obama says judges must be free to interpret the law to protect the disadvantaged and the weak against the powerful.

“The most important thing in any judge is their capacity to provide fairness and justice to the American people,” Obama said during last week’s debate.

In contrast, McCain says judges should leave policy choices to the elected branches of government.

“I will find the best people ... who have a strict adherence to the Constitution and [are] not legislating from the bench,” McCain said in the debate.

Conservative commentators have criticized Obama’s approach to judging, saying it would politicize the law and the work of judges.

“Who gets to define fairness and justice? Every person is going to have a different view of that,” says William Otis, former chief of the appellate division of the US Attorney’s Office in the Eastern District of Virginia and a commentator with the Federalist Society.

“McCain’s view is that fairness and justice are reflected in the law as adopted by the elected branches of government,” Mr. Otis says. “It is not the province of judges to rule based on their own view of fairness and justice.”

Mr. Kendall of the Constitutional Accountability Center says Obama is not seeking judges who will ignore the requirements of the law and the Constitution. “If I were instructing him about answering that question I would have referred more directly to the constitutional role of judges, but I think that is implicit in what he is saying,” Kendall says.“A big part of the [constitutional] role of judges is to promote fairness and justice, that is what the due process clause requires,” he says.

In last week’s debate, Obama cited a 2007 Supreme Court decision, Ledbetter v. Goodyear, to show how his judges and justices would rule differently than conservative jurists.

The case involved a female supervisor who received lower pay than her male counterparts. She didn’t discover the discrimination until the end of her 19-year career. But her lawsuit was thrown out of court because the law required that charges be filed within 180 days of the discriminatory pay decision.

The five-justice conservative majority adopted a narrow view of the antidiscrimination law and upheld the dismissal of her lawsuit. They said the 180-day limitation was set by Congress and that Congress could change it if it was deemed unfair, but that it was not the role of judges to rewrite the law.

The four dissenting liberal justices blasted the majority. They said it would be difficult for a victim of pay discrimination to know within 180 days that her rights had been violated. They said Ms. Ledbetter deserved to have her day in court.